1. Field of the Invention
The present invention relates to a recording apparatus for recording by causing recording means to reciprocate to correlatively scan on a recording material. A printer of the kind, the so-called serial printer, repeats the main scanning where recording means reciprocate to scan, and the sub-scanning where a recording material is carried in the direction rectangular to the main scanning direction for the performance of recording.
2. Related Background Art
A recording apparatus provided with the functions of a printer, copying machine, facsimile apparatus, and the like or a recording apparatus used as output equipment for a complex machine including a computer, a wordprocessor, or the like, or for a work station is structured to record images (including characters, symbols, and the like) on a recording material (recording medium) such as a recording sheet, a thin plastic plate (OHP sheet or the like) in accordance with image information. Depending on the recording means to be adopted, the recording apparatuses are divided into those using an ink jet method, a wire-dot method, a thermo-sensitive method, a laser beam method, among others.
In a recording apparatus of a serial type that adopts a recording method whereby to conduct its main scanning in the direction in the carrying direction of a recording material (sub-scanning direction), images (including characters, symbols, and the like) are recorded by use of recording means installed on a carriage that travels (scans) along the recording material after the recording material is set at a given recording position. After one line portion has been recorded, the sheet is fed (sub-scanned) for a given amount, and then the images on the next line are recorded by means of the main scanning. By repeating such operation, images are recorded in a desired area on the recording material. On the other hand, in a recording apparatus of a line type where recording is executed only by sub-scanning to carry a recording material in the carrying direction, the recording material is set at a given recording position, and then, the sheet feeding is conducted for a given amount (pitch fed), while a one-line portion is being recorded continuously altogether, thus recording images on the entire area of the recording material.
Of the aforesaid recording methods, the ink jet method (an ink jet recording apparatus) is the one that records by discharging ink from recording means recording head) onto a recording material, thus making it easier to fabricate recording means compactly, and to record highly precise images at high speeds. This method also makes it possible to record on an ordinary sheet without any special treatments given to it, leading to lower running costs. Being non-impact, the method makes lesser noises when the apparatus is in operation. Also, among other advantages, it is easier for this method to record images in color using ink of multiple colors. Particularly, it is possible to attain a higher speed recording by use of a recording apparatus of a line type that uses a line type recording means where many numbers of discharge ports are arranged in the sheet width direction.
Here, recording means (recording head) using an ink jet method, in which ink is discharged by utilization of thermal energy, makes it possible to easily fabricate the recording means provided with a highly densified arrangement of liquid paths (arrangement of discharge ports) by providing electro-thermal transducing elements, electrodes, walls for liquid paths, a ceiling board, and others on a base board by means of film formation technologies, which include etching, deposition, sputtering, or other semiconductor fabrication processes. Consequently, the recording means is made more compact. Also, by utilizing the advantages of IC technologies and micro-machining techniques, it becomes easier to elongate and surface the recording means (to make it two-dimensional), facilitating the provision of a multiple recording means, and the performance of a highly densified assembling thereof. Meanwhile, there are various demands on the materials of recording media. In recent years, there have been demands on use of thin papers and processed papers (such as punched sheets for filing use, scored sheets, arbitrarily shaped sheets) in addition to the sheet papers and thin plastic plates that are usually used.
In the recording apparatus of a serial type, a recording material is set at a given position. After that, images are recorded (main scanned) by driving the recording head in accordance with recording information while causing the recording head (recording means) installed on a carriage to travel along the recording material by use of a carriage motor as described above. After the completion of one line recording, the sheet is carried (by pitches) for a given amount by the rotation of a carrier roller driven by a carrier motor, and then, the images on the next line are recorded (main scanned). Such operation is repeated to record images on a recording material.
FIG. 10 is a velocity chart which shows the controlled conditions of acceleration and deceleration of a carriage motor generally used, and the actual motion of a carriage as well. In FIG. 10, the axis of ordinate represents the speeds V, and the axis of abscissa represents the positions P of the carriage. Also, in FIG. 10, the reference mark m1 designates the control of the carriage motor in recording operation in the normal mode. A reference mark m2 designates the control thereof in the draft mode where it operates at a higher speed than that in the normal mode. An area L1 is the acceleration area, while an area L3 is the deceleration area. Also, an area L2 is the recording area where recording is performed while the carriage travels. In this recording area L2, the carriage is arranged to travel at a constant speed so as to execute a high quality recording. In each of the modes ml and m2, the solid line CL represents the controlled speed of the carriage motor, while the two-dot chain line MV represents the actual movement of the carriage when it is controlled as in the condition represented by the solid line CL.
In the normal dot recording operation represented by the reference mark ml, the carriage motor is not out of step due to the controlled acceleration and deceleration. Thus it is driven to effectuate the scanning of the recording area L2 at a speed V1. Here, the draft mode is generally known as a recording mode whereby to attain low running costs by enhancing recording speeds only for the purpose of a test printing or the like, although the quality of recorded images is inevitably lowered. In FIG. 10, the draft mode represented by the reference mark m2 is such that the recording speed is enhanced two times (as shown at 2V.sub.1 in FIG. 10) with the execution of a recording by thinning out the recording dots by 50%. In this draft mode, it is difficult to set sufficient acceleration and deceleration areas because of the limited size of an apparatus. Therefore, an acute acceleration is needed. For that matter, even if the driving of the carriage motor is controlled so that the scanning may be performed at a constant speed after such acceleration, the actual movement of the carriage also results in the varied speeds in the recording area L2 shown in FIG. 10. This produces an adverse effect on the quality of recorded images, but being employed for the purpose of test printing or the like, the recording is carried out in this mode with the understanding of the user that the higher speeds are only obtainable at a slight sacrifice of the quality of recorded images.
FIG. 11 is a velocity chart which shows one example of recording control by the application of the conventional technique. The axes of ordinate and abscissa in FIG. 11 also represent speeds V and carriage positions P as in FIG. 10. A reference mark L2 designates a recording area as in FIG. 10. Here, a reference mark L4 designates a non-recording area (skipping portion). As shown in FIG. 11, the scanning speed of the carriage is enhanced in this area. It is intended to shorten the total time required for recording by increasing the main scanning speed in the non-recording area, while making the scanning speeds constant in the recording area as shown in FIG. 11, so as to effectuate a control for the performance of a skipping operation to make the period of main scanning shorter.
FIG. 12 is a view which schematically shows the factors required to determine the width of a recording apparatus. In FIG. 12, a reference numeral 1 designates a recording head; 1A, the recording unit of the recording head 1; HL, the width of the recording head; and 80, a recording material for recording to be made on. Also, a reference mark ML designates the width of an apparatus; RL, a recording width; .alpha., the acceleration and deceleration areas; .beta., the left recording blank on a recording material; and .gamma., the right recording blank of the recording material. Also, a reference numeral 1' designates a position where the recording head travels to the right hand side in FIG. 12 by means of the carriage scan.
It is desirable to make an arrangement so that the acceleration of the carriage terminates, and then, scanning is conducted at a constant speed when the recording head 1 is caused by the carriage to scan, and the recording unit 1 arrives in the recording width RL. As shown in FIG. 12, the width of the recording apparatus (apparatus width) ML is determined by the factors such as the recording width RL, the acceleration and deceleration areas a (including the constant area to stabilize the head traveling), and the width of the recording head HL. However, in the conventional art, there is a need for the stabilized driving of a motor in order to obtain a high quality in recorded images. Therefore, it is necessary to make wider the acceleration and deceleration areas at L1 and L3 in FIG. 10.
Also, regarding the recording blanks (recording width), it is usual that the left and right blanks are set at approximately 15 to 20 mm each for most of the general documents. For a printer, however, a measure is required to enable a blank to be set at as narrow as 5 mm due to occasional uses of the printer for some other special purposes. In addition to the provision of such area that may be needed occasionally, the acceleration and deceleration areas are required as described above. As a result, it is inevitable that the size of the apparatus is made larger. However, this kind of technique is rather against the trend in making the recording apparatuses smaller in recent years to meet the increasing demands on personal computers, wordprocessors, or the like, which should be more suitable for personal uses. Further, in order to solve problems of this kind, it is arranged, in some cases, to make the recording width narrower for the purpose of making the apparatus smaller; to slow down the scanning speeds in order to make the acceleration and deceleration areas smaller; or to perform recording before the stabilized driving is reached at a sacrifice of the quality of recorded images. This sort of arrangement does not present any fundamental solution of the problem described above. With such an approach as this, it is utterly difficult to obtain the user's satisfaction, of course.